1. Field of the Invention
This invention relates, in general, to apparatus and methods for handling workpieces and, in particular, to apparatus for transferring workpieces to and from a workstation. The invention relates especially to apparatus an methods for automatically loading and unloading printed circuit board panels onto and off of the tooling plate of a computer controlled drilling machine.
2. Prior Art
The drilling operations performed in conjunction with manufacturing printed circuit board panels are required to be performed to very precise tolerances. These drilling operations are performed with a computer controlled drilling machine under automatic numerical control and may typically involve thousands of drilling operations per panel. In a typical application, the printed circuit board panels are placed on a horizontal work platform or tooling plate located below the drill spindle. The panels are typically stacked up to three or four high on the tooling plate of the drilling machine so that several panels are drilled at the same time. Inasmuch as the spindle must be able to reach any point on the panels, relative movement in three dimensions is required between the spindle and the panels. This requirement has been implemented in various ways.
In a common drilling machine design, the machine table moves in one horizontal dimension and the drill spindle moves in the orthogonal horizontal dimension. In addition, the drill spindle moves in the vertical dimension. In other designs, for example, the tooling plate may be configured to move in both horizontal dimensions or even vertically or the drill spindle may move in additional dimensions.
Recent trends and increased competition in manufacturing circuit panels have created a need for increased efficiency and cost reduction in the manufacturing process. The batch sizes have been getting smaller and are predicted to get still smaller in the future. However, a manufacturer is required to be flexible enough to handle these small batch sizes. Although the drilling process is already highly automated, increased automation of the process may further reduce the need for operator action or intervention.
For many years the panels have been hand loaded (and hand unloaded) onto the tooling plate of the drilling machine. This hand loading of the panels onto the tooling plate requires time consuming and expensive operator intervention. One method of increasing the efficiency and reducing the cost of the drilling process is to reduce the time and operator demands of the loading and unloading process. In a typical manufacturing operation, multiple drilling machines are operated simultaneously. Thus, a reduction in the operator work load will allow fewer operators to operate more drilling machines.